It seems like a bit of a pain to build WebKitGTK on Windows. WebKit itself seems to support Windows, but I'm not sure if WebKitGTK does.
If WebKitGTK doesn't support Windows, feel free to close this issue. If that's the case, could you refer me to any tickets/issues/docs about WebKitGTK not supporting Windows? I haven't been able to find a statement either way.